1. Field of the Invention
The invention relates to a variable compression ratio internal combustion engine that varies its compression ratio, and in particular to a drain structure for discharging coolant from a variable compression ratio internal combustion engine and a method for discharging coolant from a variable compression ratio internal combustion engine.
2. Description of the Related Art
In recent years, for the purpose of improving the fuel economy and the output performance of an internal combustion engine, technologies for variably controlling the compression ratio of an internal combustion engine have been proposed. One of such technologies is described in Japanese Patent Application Publication No. JP-A-2003-206771. In an internal combustion engine recited in this publication, the cylinder block and the crankcase are connected to each other such that the cylinder block can be moved relative to the crankcase and a camshaft is provided at the connecting portion between the cylinder block and the crankcase. As the camshaft is rotated, the cylinder block is moved relative to the crankcase in the axial direction of the engine cylinder, so that the capacity of the combustion chamber changes and thus the compression ratio of the internal combustion engine varies.
When manufacturing a variable compression ratio internal combustion engine configured as described above, after the engine bench test in pre-shipment inspection, it is often the case that the engine coolant that has been used in the engine bench test is discharged from the engine in order to prevent corrosion of the cylinder block of the engine. Also, in some maintenance work for such a variable compression ratio internal combustion engine, the coolant is discharged from the engine.
However, the above-described variable compression ratio internal combustion engine in which the relative positions of the cylinder block and the crankcase are changed to vary the compression ratio is often configured such that the cylinder block is moved relative to the crankcase with a portion of the cylinder block being received in a receiving portion that is formed as a portion of the crankcase. In this structure, the outer wall of the cylinder block is covered by the outer wall of the receiving portion of the crankcase. Thus, if a drain hole for connecting the water jacket and the outer side of the cylinder block is simply formed, the coolant may not be guided to the outer side of the crankcase, that is, the coolant may not be appropriately discharged.